Search For Answers Begins Following Deadly Shootings

NPR justice correspondent Carrie Johnson joins us in the studio for more on the investigation. Carrie, thanks for being with us.

CARRIE JOHNSON, BYLINE: Thank you, Scott.

SIMON: What do we know about the shooter, and is anything developing on what I noticed Lieutenant Vance carefully called - he didn't use the word motive, he said the how and the why of the shooting?

JOHNSON: We know the shooter is Adam Lanza. Federal law enforcement authorities have been confirming that for us. He's a 20-year-old. He died at the scene, at the school. Lt. Paul Vance says he's still holding his cards close to his chest. But they've uncovered some good evidence as to how, and more importantly, why this crime occurred. He didn't want to describe the nature of that evidence. As a law enforcement reporter for a long time, I'm wondering and want to ask as the next news conference: were there any notes, any clues, anything on the shooter's body that might help us understand?

SIMON: Anything to indicate, at this point, that the gunman did not act alone?

JOHNSON: Authorities say there have been no other arrests. That's really important because early on, yesterday, in the course of this tragedy, it had been misreported that Adam Lanza's brother had been arrested. Adam Lanza's brother is cooperating with authorities. He's helping them to try to understand what was going on.

SIMON: He was brought in for questioning in Hoboken and the unfortunate video people saw of him in handcuffs. But he turns out to be not related to the case.

Yes. No one else has been arrested in connection with this crime.

And the secondary crime scene, what is now acknowledged to be officially the death of the mother at what's being described as a family home. What do we know about that?

JOHNSON: That residence is owned by Nancy Lanza, according to property records, the mother of Ryan and Adam Lanza, the suspected shooter. It was sold to Nancy Lanza by her ex-husband for something like a dollar a year ago, after their divorce. And investigators have been swarming that neighborhood and have that locked down as a crime scene as well.

What I'm wondering at this point is the elapsed time between the killing of Nancy Lanza and the shootings at the school.

SIMON: And what do we know about the weapons? Reportedly, there have been three weapons that the shooter brought to the school. Did he bring all of them in? What do we know about these weapons?

JOHNSON: We know now, according to federal law enforcement sources, that three weapons were found on or near the body of the shooter at the school; two pistols, a semiautomatic - a Glock and a Sig Sauer. And also a .223 caliber Buckmaster rifle. This is a very lightweight semiautomatic rifle, also the kind of weapon used by the D.C. sniper shooters years ago.

All of these weapons had been legally purchased and registered to Nancy Lanza, the mother of the suspected gunman, Adam Lanza.

Carrie, you look forward to what's going to be happening over the next 24 and 48 hours, of course, and beyond. What key questions do you thing authorities are going to try to begin to answer today?

The question, not just for law enforcement, not just for these Connecticut state police, FBI and the ATF on ground, but the question on everyone's mind is why did this young man target a school and children aged five to 10 years old? What was going on in his mind that led him to drive to the school armed to the teeth?

Also wondering if he had an advance of this deadly attack sent out any clues, talked to anybody - friends, relatives, neighbors - about his plans, or used social media; Twitter, Facebook, email. Authorities have been executing search warrants for the last 24 hours. They're obviously going to be looking at any computers and electronic accounts this young man had.

Finally, some concern about other traps or incidents that may have been put into works by this gunman...

SIMON: And we should explain. There's been a history of this. Even just very recently, hasn't there?

JOHNSON: Unfortunately, Scott, after the Aurora, Colorado theater shootings, authorities discovered that suspect's apartment had been booby-trapped, and it took them hours to defuse those explosives. There's no hint of that here right now in Newtown, Connecticut, but the fact of the matter is that authorities always have to be worried about that kind of situation as well.

SIMON: Yeah, now, have people noticed that immediately when the last name began to come out, people began to check Facebook profiles. Is there some feeling that people who are reportedly alienated and closed off sometimes use social media as a way of announcing their grievances, if not their intentions?

JOHNSON: Not always. Not always, Scott, but given the fact that so many of use electronic media as a part of our daily life, and as an extension of our personalities in our hands, it's a very important tool for investigators in these kind of cases.